A last-gasp strike from Kevin Betsy earned the Blues a breathtaking 3-2 victory in the Bucks derby, after Gary Waddock's side had twice been pegged back by the Dons in a dramatic clash at stadiummk.
Alex Revell's smart side-footed finish looked to have given the visitors a half-time lead before Aaron Wilbraham's stoppage time leveller, but Revell slotted home after the break from a Betsy through-ball.
Wilbraham equalized again when he pounced first after Tom Heaton had parried Sam Baldock's harshly-awarded penalty, but Wycombe's never-say-die attitude paid dividends yet again deep into injury time.
After a chaotic series of events inside the area, the ball fell to Betsy, who kept the coolest head in the stadium to see his deflected effort find the net and spark delirium in the away end.
Gary Waddock named an unchanged XI from Tuesday's 3-0 triumph at Tranmere, which meant thatAlex Revell, who scored twice at Prenton Park, started up front alongside Jon-Paul Pittman, while Lewis Hunt continued at centre-back alongside Chris Westwood.
MK Dons recalled former Wanderer David McCracken after suspension but there was no room for another ex-Blue, Jermaine Easter, who missed out through injury.
Both sides were welcomed into a cauldron noise at stadiummk but it was Wycombe who settled the better of the two Buckinghamshire rivals.
Firstly Jon-Paul Pittman saw a 20-yard effort deflect wide of Willy Gueret's right-hand post before Matt Bloomfield smashed a shot over the top after the ball had fallen loose on the edge of the Dons box.
But the best chance of the opening exchanges fell to MK striker Sam Baldock who, after wriggling away from John Mousinho, flashed a drive just wide of Tom Heaton's goal.
That seemed to liven up the hosts and ex-Manchester United midfielder Luke Chadwick tested Heaton after a mazy run from the halfway line.
However, Gary Waddock's Wanderers responded and a quick throw from Alex Revell set Ainsworth free down the right. The midfielder outpaced Mathias Doumbe before sending a teasing ball across the face which had to be cleared in front of the lurking Kevin Betsy.
Just before the half hour mark Wycombe did take the lead and it came courtesy of that man Alex Revell. Betsy latched onto Lewis Hunt's free-kick down the left before pulling the back to Revell, who finished smartly into the bottom right-hand corner from just inside the Dons box.
At the other end, Baldock glanced an effort wide of goal before Wilbraham headed straight into the grateful arms of Heaton after meeting Chadwick's cross.
Moments later and the Blues went within inches of going 2-0 ahead. Woodman's corner caused mayhem in the Dons box and Dan Woodards was forced to clear off the line after Lewis Hunt had beaten Doumbe in the air.
And they were made to pay for that miss when Wilbraham leveled matters on the stroke of half-time. Mark Randall's floated free-kick was allowed to travel all the way to the back post, where the striker was gifted the easy chance to tap home with virtually the last kick of the half.
There were no changes at the break, and Gareth Ainsworth showed Wycombe's intent with a darting run into the box within seconds of the restarts, although he was denied a shooting opportunity by a last-ditch block.
At the other end, Adam Chicksen bent a long-range effort over the bar following a corner that should never have been given, but the best chance of the half fell to Jon-Paul Pittman when he failed to convert in a one-on-one situation.
Matt Bloomfield laid the ball on a plate for the striker to charge into the Dons' box, but after slipping the ball under the keeper, Pittman was devastated to see the ball roll the wrong side of the post.
Danny Woodards was injured whilst fouling Kevin Betsy in the build-up and needed to be replaced by Sol Davis, while fellow defender Dean Lewington drilled straight at Tom Heaton on 58 minutes.
The drama kept coming, and Wanderers were in front again on 62 minutes courtesy of Revell's second of the game. Lewis Hunt made a stunning block inside the Blues box and the visitors quickly broke though Kevin Betsy, whose through-ball was slotted home perfectly by the in-form striker.
But the Dons upped the pressure and won a penalty on 73 minutes when Ainsworth was adjudged to have fouled Luke Chadwick in a 50/50 challenge in the box. Referee Mathieson gave it, and although Tom Heaton saved superbly from Sam Baldock's spot-kick, Wilbraham scored with the rebound despite the best efforts of Heaton on the line.
Wycombe's response was to bring on Stuart Beavon in place of Lewis Montrose, and the replacement almost flicked home Kevin Betsy's cross in a goalmouth scramble, before Matt Phillips was denied a shooting chance by Sol Davis.
Beavon then fired wide of the near post after another Revell knock-on, and only the referee will know why he didn't send off Luke Chadwick for a second yellow card when he hacked down Matt Phillips on the edge of the box.
Alex Revell's free-kick was deflected over the top as Wycombe pressed desperately for the winner, and Stuart Beavon's powerful drive flew just past the post as the clock ticked towards 90.
Dean Lewington then cleared Matt Phillips' cross off the line in stoppage time and Beavon once again shot wide, but the glory was saved for Betsy, who stole the headlines with a deflected effort with the last kick of the game.